240 SPECIAL SENSES. 



motor nerve probably through the salivary glands in moist- 

 ening the gustatory membrane. 



As we have already remarked, it is difficult to determine 

 the exact origin of the filaments of the chorda tympani. 

 They may come from the root called the nerve of "Wrisberg, 

 but this has not been positively established, either anatomi- 

 cally or physiologically ; but the course of the nerve, after it 

 has joined the lingual branch of the fifth, is sufficiently clear, 

 as we have seen. Schiff, who supposes that the filaments 

 presiding over the sense of taste are derived originally from 

 the fifth, assumes that these filaments " emerge from the 

 cranium with the second branch of this nerve, enter the 

 spheno-palatine ganglion," and then pass to the third branch 

 by a course which is as yet undetermined. 1 If this be the 

 fact, and the idea is based chiefly upon physiological grounds, 

 extirpation of the spheno-palatine ganglia should abolish the 

 sense of taste in the anterior portion of the tongue. Al- 

 though the operation of removal of both these ganglia is 

 difficult, this has been done successfully by Prevost, who 

 denies that such a mutilation has any effect upon gustation. 2 



As a summary of our knowledge regarding the gustatory 

 properties of the anterior two-thirds of the tongue, certainly 

 in the human subject, it may be stated without reserve, that 

 these properties depend upon the chorda tympani, its gusta- 

 tory filaments being derived from the facial, and taking their 

 course to the tongue with the lingual branch of the inferior 

 maxillary division of the fifth. In addition, the lingual 

 branch of the fifth contains filaments, derived from the large 

 root of this nerve, which endow the mucous membrane with 

 general sensibility. 



Glosso-Pharyngeal (First Division of the Eighth). The 

 glosso-pharyngeal is distributed to those portions of the gus- 



1 SCHIFF, Digestion, Florence et Turin, 1867, tome i., p. 140. 



2 PREVOST, Nouvelles experiences relatives aux fonctions gustatives du nerf lin- 

 gual. Archives de physiologic, Paris, 1873, tome v., p. 387. 



